Today's counterfeiters are shrewd and technically savvy. Advances are needed to complicate the counterfeiter's efforts. Moreover, some of today's watermarking applications require additional data carrying capacity.
One solution is to embed steganographic auxiliary data variously in multi-channels carried by an object.
One form of steganography is digital watermarking. Digital watermarking systems typically have two primary components: an encoder that embeds a watermark in a host media signal, and a decoder (or reader) that detects and reads the embedded watermark from a signal suspected of containing a watermark. The encoder can embed a watermark by altering the host media signal. The decoding component analyzes a suspect signal to detect whether a watermark is present. In applications where the watermark encodes information, the decoder extracts this information from the detected watermark. Data can be communicated to a decoder, e.g., from an optical sensor (e.g., a web camera, digital camera, scanner, etc.).
A watermark can have multiple components, each having different attributes. To name a few, these attributes include function, signal intensity, transform domain of watermark definition (e.g., temporal, spatial, frequency, etc.), location or orientation in host signal, redundancy, level of security (e.g., encrypted or scrambled), etc. The components of the watermark may perform the same or different functions. For example, one component may carry a message, while another component may serve to identify the location or orientation of the watermark. Moreover, different messages may be encoded in different temporal or spatial portions of the host signal, such as different locations in an image or different time frames of audio or video. In some cases, the components are provided through separate watermarks.
The physical manifestation of watermarked information most commonly takes the form of altered signal values, such as slightly changed pixel values, picture luminance, picture colors, DCT coefficients, instantaneous audio amplitudes, etc. However, a watermark can also be manifested in other ways, such as changes in the surface microtopology of a medium, localized chemical changes (e.g. in photographic emulsions), localized variations in optical density, localized changes in luminescence, etc. The surface texture of an object may be altered to create a watermark pattern. This may be accomplished by manufacturing an object in a manner that creates a textured surface or by applying material to the surface (e.g., an invisible film or ink) in a subsequent process. Watermarks can also be optically implemented in holograms or embedded in conventional paper watermarks.
Some techniques for embedding and detecting watermarks in media signals are detailed in the assignee's U.S. Pat. Nos. 6,122,403 and 6,614,914, and in PCT patent application PCT/US02/20832 (published as WO 03/005291), which are each herein incorporated by reference.
In the following disclosure it should be understood that references to watermarking and steganographic hiding encompass not only the assignee's technology, but can likewise be practiced with other steganographic technologies as well.
According to one aspect of the present invention an identification document includes a photographic representation of a bearer of the document and indicia printed thereon. The identification document further includes a first digital watermark component conveyed through a first channel which is visibly perceptible under visible lighting conditions; a second digital watermark component conveyed through a second channel which is substantially non-visible under visible lighting conditions, but at least a portion of the second channel becomes visible with infrared illumination; and a third digital watermark component conveyed through a third channel which is substantially non-visible under visible lighting conditions, but at least a portion of the third channel becoming visible with ultraviolet illumination.
Another aspect of the present invention provides a method of authenticating a physical object. The object includes a first digital watermark conveyed through a first channel and at least a second digital watermark conveyed through a different, second channel. The first digital watermark includes a first orientation component conveying a first orientation and the second digital watermark includes a second orientation component conveying a second orientation. The first orientation is different than the second orientation. The method includes: receiving optical scan data representing at least some of the object; analyzing the optical scan data to recover the first orientation component and the second orientation component; determining, based at least on the first orientation component and the second orientation component, the first orientation and the second orientation; and deciding whether the object is authentic based on at least one of the first orientation and the second orientation.
Yet another aspect of the present invention is a method of conveying auxiliary data through digital watermarking. The method includes: providing a first digital watermark signal comprising a first orientation component; providing a second digital watermark signal comprising a second orientation component; conveying the auxiliary data through a relative orientation relationship of the first orientation component and the second digital watermark component.
The foregoing and other features, aspects and advantages of the present invention will be even more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.